Borda–Carnot equation ( in relation to Bernoulli's principle)


Borda–Carnot equation is an empirical description of the mechanical energy losses of the fluid due to a (sudden) flow expansion. It describes how the total head reduces due to the losses. This in contrast with Bernoulli’s principle for dissipationless flow (without irreversible losses), where the total head is a constant along a streamline. In case of high-pressure pipe flows, when gravitational effects can be neglected, the fluid’s mechanical energy loss is related to potential energy density due to gravity, the loss of pressure and the flow velocities of the fluid.

Related formulas


ΔE The fluid's mechanical energy loss per unit of fluid volume (J/m3)
p2The pressure at location 2 (Pa)
p1The pressure at location 1 (Pa)
ρThe fluid density (kg/m3)
v2The mean flow velocity after expansion (m/s)
v1 The mean flow velocity before expansion (m/s)